Stainless steel has been so far used as a metallic sheet for rubber-metal laminates directed to engine cylinder head gaskets. Rubber-metal laminates formed by vulcanization-bonding rubber on the stainless steel by direct application of a vulcanizable adhesive thereto have such problems as unsatisfactory adhesiveness, and heat resistance or liquid resistance.
To solve the problems, several methods for improving the adhesiveness between stainless steel and rubber by subjecting a primary treatment to the surface of stainless steel have been so far proposed, including, for example, a method for subjecting a coating type chromate treatment or phosphate treatment to the surface of stainless steel. Particularly in the gasket use, a coating type chromate treatment involving hexavalent chromium ions designates as a specific chemical substance has been generally used to improve the primary rust prevention and the adhesiveness, but the coating type chromate treatment involves such Cr ions and thus is environmentally not preferable.    Patent Document 1 JP-A-11-221875    Patent Document 2 JP-A-2000-6308
The present applicants have so far proposed various vulcanizable adhesive compositions or phenol resin-containing adhesives on the basis of an alkoxysilane as an adhesive for use between metal and nitrile rubber.    Patent Document 3 JP 3,669,973    Patent Document 4 JP-A-2003-334885    Patent Document 5 JP-A-2004-76699    Patent Document 6 JP-A-2004-277435    Patent Document 7 JP-A-2004-11576
These adhesives can attain the desired object as chromium-free adhesives, i.e. involving no hexavalent Cr ions, but still have a problem such as special considerations being required for applicable rubber species when compounding. The tight adhesiveness can be obtained between metal and rubber, but the heat resistance is still not satisfactory, even if well known hydrogenated nitrile rubber having a distinguished heat resistance is used. Furthermore, there is still room for improvement with respect to rubber bulging resistance (rubber flow resistance), when used at elevated temperatures and surface pressures.